Field of the Invention
The present invention relates to a voltage supply circuit included in a terminal equipment, and more specifically, to a voltage supply circuit included in a terminal equipment, in which the voltage supply circuit includes a variable circuit unit for preventing a pop-up phenomenon generated by abrupt change of voltage when the terminal equipment supplies the voltage to an earphone device.
Background of the Related Art
An earphone device allows a user to listen to music or broadcast regardless of time and space without hindering other people when the user listens to audio using a terminal equipment. Generally, an earphone system for operating an earphone device is a system allowing a terminal equipment to sense connection of an earphone according to change of state of the head of the earphone device electrically connected to the earphone connection interface of the terminal equipment.
Active noise cancelling techniques (ANC) are introduced recently to improve quality of sound of the earphone device. The active noise cancelling technique (ANC) is a technique of analyzing frequencies, magnitudes, sound qualities and the like of various kinds of sounds flowing into the earphone device and offsetting noises by sending out sound waves of reverse wavelength through a speaker. Such an active noise cancelling technique (ANC) is stated in the ‘Active Noise Cancelling System’ disclosed in Korean Patent Publication No. 10-2011-0097622.
However, in order to apply such an active noise cancelling (ANC) technique to an earphone device, voltage should be supplied to the earphone device through the interface of the terminal equipment, and there is a problem in that a noise pop-up phenomenon occurs due to change of voltage when the voltage is supplied.